I run a league on Fanball and I'm humbled by the prospect of how out of hand "create your own rules" leagues can get. There can literally be thousands of feature points. And sure, you can put together a simple fantasy site easily, but there's still a steady creep of features you want to have. So I could see how that would be the case.

I imagine you guys are using Rails and ran into the same issue I did with my real estate statistics, which is that there is no particular framework for running and caching "baked" statistics over data in Rails. I've thought about how to generalize and abstract some of the stuff I've done with that into a plugin, but it's probably not going to happen anytime soon.